This invention relates to the protection of compressors in heating, cooling, or refrigeration systems. In particular, this invention relates to apparatus for protecting these compressors from adverse environmental conditions.
Compressors in heating, cooling, or refrigeration systems may have to operate in less than optimal environments. For example, a compressor in a heat pump may be required to provide heat to an interior space when the compressor is operating in a cold outside environment. There may also be situations in which cooling is required of an interior space when the compressor is operating in an outside temperature environment that is rather cold. An example of an even harsher environment for a compressor can be found in situations experienced by a transport refrigeration system. These latter systems are often called upon to cool or refrigerate a cargo being transported by a truck, train locomotive or other transport means in a variety of adverse weather conditions.
The oil used to lubricate these compressors is particularly vulnerable to such cold environments since it may become quite viscous at low temperature if the compressor has not been operated for a significant period of time. The oil might also be holding refrigerant picked up from various parts of the compressor. Circulating this oil through the compressor can cause damage to the compressor. In this regard, the oil will not properly lubricate critical parts of the compressor causing them to deteriorate much faster than would otherwise be the case.
Heretofore, the lubricating oil has been maintained at an appropriate temperature by various electrical heating devices either mounted inside or outside of the housing that holds the oil. This housing is often referred to as the crankcase in many compressor configurations. These heating devices consume electrical energy when electrical current flows in the circuits associated with these devices. These heating devices moreover may not operate properly from time to time due to a breakdown in the circuit carrying the electrical current.
It would be preferable to have a source of heat that would not require a significant amount of energy. It would furthermore be preferable that the source of heat not be susceptible of breaking down at a critical time when a demand is being placed on the compressor by the heating, cooling, or refrigeration system.